1. Field of the Invention
The present invention relates to an auxiliary air control valve for engines, which can bypass a throttle valve in the intake passage of an internal combustion engine to control the supplied quantity of intake air.
2. Discussion of Background
There has been known a system wherein an internal combustion engine has a throttle valve arranged in an intake passage, and has fuel supplied in the form of injection by a fuel injection valve arranged in an intake manifold.
In that system, in order to prevent idling from being unstable at low temperatures, the arrangement of an auxiliary air control valve in a passage bypassing the throttle valve allows intake air to pass through the passage at low temperatures, thereby slightly increasing idling engine speed. On the other hand, when the engine is at high temperatures, bubbles can generate in the fuel within a delivery pipe of a fuel injector to deteriorate restart of the engine. It has been known that the auxiliary air control valve has a device which can pass bypassed intake air even at high temperatures, and that idling engine speed at high temperatures is slightly increased for easy restart of the engine.
As such a prior art reference, there is e.g. Japanese Unexamined Utility Model Publication No. 183043/1987. The conventional auxiliary air control valve disclosed in that publication is shown in section in FIG. 5. In FIG. 5, reference numeral 1 designates an auxiliary air control valve (hereinbelow, referred to as "the air control valve"). Reference numeral 2 designates a valve casing which has a one end portion formed with an inlet 3 for introducing a part of the cooling water for the engine and an outlet 4 for returning the introduced part of the cooling water to a cooling water pump of the engine. The valve casing 2 also has the other end portion formed with an air inlet port 5 and an air outlet port 6. The air inlet port 5 is connected to an introducing bypass passage which communicates with a location of an intake passage to the engine upstream of a throttle valve (not shown) arranged in the intake passage. The air outlet port 6 is connected to a return bypass passage which communicates with a location of the intake passage downstream of the throttle valve.
Reference numeral 7 designates a temperature dependent type actuator which is fixed in the valve casing 2, and which hermetically contains thermowax which expands and contracts depending on the temperature of the cooling water from the engine. The actuator 7 is provided with a cylindrical portion 8. Reference numeral 9 designates an operating rod which is supported in the cylindrical portion 8 so as to be axially movable, and which is protruded depending on the expansion of the thermowax. Reference numeral 10 designates an annular partition which is fixed in the valve casing 2, which separates an air inlet side and an air outlet side in the valve casing 2, and which has a valve seat port 10a formed therein. Reference numeral 11 designates a valve rod which has its rear end portion provided with a sleeve to be slidably supported by the cylindrical portion 8, and which projects depending on the protrusion of the operating rod 9. The leading edge of the valve rod 11 extends to the position where the partition 10 is located, and has a retaining ring 12 fitted in its end. The valve rod 11 has a groove 13 formed therein to axially extend. Reference numeral 14 designates a valve which is slidably carried on the valve rod 11, which has its periphery faced to the valve seat port 10a with a small gap, and which has its leading portion tapered.
The sleeve of the valve rod 11 has a spring seat 15 mounted thereto, and a spring 16 is arranged between the spring seat 15 and the partition 10 to urge the valve rod 11 in a retracted or backward direction. The valve 14 is urged against the retaining ring 12 by a spring 17 which is arranged between the valve 14 and the spring seat 15.
In FIG. 5, there is shown the operating state wherein the cooling water is at an intermediate temperature. The heat expansion of the thermowax moves the operating rod 9 forth (in the rightward direction in FIG. 5), followed by forward movement of the valve rod
11 As a result, the periphery of the valve 14 confronts the valve seat port 10a to restrict the quantity of air introduced into the bypass passage to an amount which is near to zero.
When the cooling water is at low temperatures, the heat contraction of the thermowax makes the operating rod 9 retractable. The valve rod 9 is retracted by the spring force of the spring 16. As a result, the valve 14 which is carried on the valve rod 9 is retracted, and the tapered edge confronts the valve seat port 10a, thereby allowing the inspired air to fully pass through the bypass passage.
On the other hand, when the cooling water is at high temperatures, the extent of the heat expansion of the thermowax is greater than the case of FIG. 5, and the operating rod 9 is moved further forth than the case of FIG. 5. As a result, the valve rod 11 is moved further forth against the action of the spring 16 though the valve 14 is stopped by the partition 10 on the way to be prevented from moving forth. Because the valve rod 11 can move further forth than the valve 14, the groove 13 communicates the air inlet side to the air outlet side to allow the introduced air to pass through the bypass passage.
In that manner, the quantity of the air introduced into the bypass passage is controlled depending on the cooling water temperature (corresponding to the temperature of the engine) as shown in FIG. 6. This arrangement facilitates starting even if the engine is at low temperatures or high temperatures.
The conventional air control valve stated earlier requires the provision of the groove 13 in the valve rod 11, the machining of the groove 13 being very complicated. The valve rod 11 has to be combined with the valve 14 which is a separate part. Two kinds of the springs 16 and 17 are also needed. It creates problems in that the number of required parts is great, the structure is complicated, the production cost is high, and the size is large.